Carburetor



J. R. FISH CARBURETOR July 30, 1957 2 Sheets-Sheet 1 Filed Jan. 14. 1954 Unite CARBURETOR Application January 14, 1954, Serial No. 403,979

12 Claims. (Cl. 261-34) My invention relates to carburetors particularly suitable for providing gasoline in metered amounts to the intake manifold of an internal combustion engine.

A general object of my invention is to improve the re liability and accuracy of fuel and air metering of internal combustion engine carburetors.

A further object of my invention is to provide a carburetor having a minimum of simplified adjustment arrangements but which may be readily adjusted for operation in connection with engines of a very wide range of displacement and horsepower characteristics, and a carburetor which, when adjusted for any engine within the range, will perform at high efiiciency.

An additional and more specific object of my invention is to improve the operation and simplify the construction of carburetors of the type comprising a throttle located at the throat of the main air passage and wherein fuel is supplied through the throttle shaft and introduced into the air stream at the throttle.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings, in which:

Fig. l is an exploded perspective view of a carburetor in accord with my invention;

Fig. 2 is a fragmentary broken away view of a lower end portion of the fuel supply arm of the carburetor;

Fig. 3 is a partially cut away side view of the assembled carburetor of Fig. 1;

Fig. 4 is a partially cut away end view of the carburetor showing details of the fuel supply arm and chamber;

Fig. 5 is a top view of the carburetor partially broken away to show details of the throttle and the throttle control arrangement, and details of a vacuum spark control arrangement and of a low speed adjustable air bypass arrangement;

Fig. 6 is a fragmentary sectional view taken through the throttle and showing the throttle in closed or idling position; and

Fig. 7 is a fragmentary sectional view showing the throttle in fully open position.

As seen in Fig. 1, the carburetor comprises a main body member 1 shaped internally to form a venturi passage between an upper air inlet portion 2 and a lower outlet portion arranged for connection, by means of flange 3, to the intake manifold of the engine. Within the main air passage of the body, at a venturi or constricted throat portion, a throttle 4 is disposed, the throttle being carried on a throttle shaft 5 to be rotated between an approximately horizontal idling position and an approximately vertical full throttle position. A stop member 6, having a protrusion 7 adapted to meet an idling adjustment screw 8 mounted on the carburetor body, is arranged to be slipped over shaft 5 and to be locked in position thereon by a throttle link 9. Spring 10 is interposed between States Pater 2,801,085 Patented July 30, 1957 member 6 and the carburetor body to urge link 9 and member 6 away from the body and thus to urge shaft 5 in the direction toward the left in Fig. l.

The end of shaft 5 opposite to that at which the link 9 is attached carries a fuel supply arm 11. The arm 11 operates in a fuel supply chamber 12 formed with a substantially flat vertical wall 13 against and end of the body .1. The wall 13 is approximately the shape of a sector of a circle, and arm 11 sweeps arcuately back and forth across the surface 13 with opening and closing throttle and throttle shaft movements. A wall plate 14 is adapted to fit within the edges 15 of the walls of chamber 12 against a recessed surface 16, and the wall plate 14 seals against surface 16 and seals, with sufiicient clearance for a running fit, against arm 11 and completes the closed fuel supply chamber 12. It will be understood that the clearance between arm 11 and wall 14 is sufficient to permit free swinging, yet sufiiciently small to cause the arm to function as a vane pump in the chamber 12. Fuel, such as gasoline, is admitted through wall plate 14 into the chamber 12 through ports 17 and 18, the latter port having a flap or feather valve member 19 arranged to permit pressure to be built up by swinging of arm 11 and to prevent the flow of gasoline from the respective portion of the supply chamber when sufficient pressure is produced to seat the valve member 19 to close port 13.

As so arranged, the arm 11 divides sectorial chamber 12 into two separate sectorial compartments having respective volumes which vary inversely, in accord with the angular position of arm 11, one such compartment lying in what will be herein considered to be in advance of or ahead of the arm 11 and the other lying behind the arm. The forward compartment formed ahead of the arm serves primarily to supply an increased fuel charge to the intake air stream during acceleration and has two communications with the carburetor barrel, one through a passage 26 in the fuel supply arm and the other through an acceleration nozzle hereinafter described and shown best in Fig. 3. The rearward compartment behind the arm 11, together with the forward compartment, normally, during constant power periods, supplies fuel to the air stream through the passage 20 of the arm only. The fuel passing through passage 20 enters the throttle shaft 5 and is expelled into the air stream through vaporizing ports, such as the ports 21, shown in dotted lines, these ports being drilled in the throttle shaft to intersect the central opening of the throttle shaft.

Metering of the fuel from chamber 12 into the air stream is accomplished by a combination of a metering groove 22 formed into the wall 13 of the chamber and of a needle restriction valve controlled by an adjusting screw 23, and in other Ways as hereinafter more particularly described. The groove 22 is seen to increase gradually in size, preferably both as to width and depth, from its left hand end as seen in Fig. l to its right hand end. Gasoline entering channel 20 of the arm must pass through groove 22, and the flow is more restricted when arm 11 is at the position corresponding to idling throttle position than when the arm is at full throttle position. The groove 22 extends at least throughout the full distance traversed by the arm 11 and, preferably, extends at its larger end beyond the extreme full throttle position of the arm. The groove may also extend beyond the extreme closed throttle position of the arm 11.

The hub 24 formed at the upper end of arm 11 serves to attach the arm to the end of hollow throttle shaft 5 and a projecting vane 25 is carried by the hub to engage, in a running fit, against the cylindrical arcuate surface 26 which surrounds the hub through about 260 degrees. Vane 25 and the hub 24 form, with the balance of arm 11, a seal, within the limits of the running fit, between the forward and rear compartments of chamber 12. The small cylindrical extension of the chamber bounded by walls 26 is desirable to permit communication between the accelerating nozzle and the chamber at a point above the normalfuel level. The cylindrical extension of the chamber further permits a pressure equalizing connection between the ,fuelsupply; chamber and the float reservoir, above the normalfuel level in each, through a small aperture plate 14.

A float reservoir 28 is arranged to fit against edges 15 27 provided in of the fuel supply chamber body, a sealing gasket 29 being.

interposed. Float 30 within the reservoir controls the fuel level therein by means of a float valve 31 prefer; ably'comprising a caged ball 32 to seal against a seat within the valve body. The ball 32 is arranged to rest against a generally horizontal portion 33 of a hinge. member which pivotally supports float 29 from a sta-. tionary pin 34. A post 35 extends from the bottom of float 29 and limits downward pivoting of the float about pin 34, thereby to retain ball 32 in the cage at the lower end of the body of valve 31. A seat for the ball 32' is provided above the ball and within the body of the valve,

' and raising of the float on its pivot on pin 34 serves to raise the ball, thereby to tend to close the valve and to limit or stop the flow of fuel into the float reservoir from a supply line'connecting with the valve 31 through suitable coupling 36. a

An upstanding hollow hood 37 at the top of the 'reservoir body 28 aligns with a channel 38 of the carburetor sage 20 which terminates at the lower portion of the. arm in a short transverse passage 41 opening through the inner face 42 of the arm. The inner face of the arm in formed to lie closely against the inner wall of the fuel supply chamber, shown as wall 13 in Fig. l, and if the wall-13 has a recessed portion, as at 43 in Fig. 1.

along the fuel metering groove 22, thelower portion of face 42 of the arm should protrude into such recessed portion to provide engagement with running fit between the face 42 and the wall 13 from one end to the other.

of arm 11. The fit of the arm against the recessed sur face 43 is preferably a very close running fit.

The point at which passage 41 opens through face 42 is positioned. to face and communicate with metering groove 22,. and with swinging of arm 11, this point traversesrthe groove. A second channel 44 is provided in the lower end of arm 11 to open through face 42 at a second point also facing groove 22, and channel 44 communicates with the groove at face 42 at a point just behind or to' the rear of the point of communication of passage 41, and furnishes a connectionin the nature of a bypass connection between this rearward point on face 42 and the forward face 45 of arm 11. The provision of a small'downward projection 46 on the lower end of armll permits the arm' substantially completely to seal, as permitted by the running fit, between the forward compartment of chamber 12 lying ahead of for-. ward face 45 of the arm and the rearward compartment lying behind rear face 47 of the arm, the only communication, normally, between the chambers being through. the short length of the groove 22' which is covered by face 42, and also through a short portion of this covered length and through bypass channel 44 in sequence Fig. 3 is a side view ofthe assembled carburetor almostentirely.insection. Link 9 is aflixed at the control end of throttle shaft.5 and clamps stop member 6 to the shaft. Adjustable screws 8 and 48 on the carburetor body 1 are arranged to cooperate with protrusion '7 of the stop member to adjust the extreme idling and full throttle positions of shaft 5, and, accordingly, the extreme positions of the throttle and arm.

Fuel supply arm 11 is aflixed, preferably in a pressed fit, at the end of throttle shaft 5 opposite to link 9 and by means of a suitable set screw 49, and compression spring 10 urges shaft 5 longitudinally in the direction to retain inner surface 42 of arm 11 in a running fit against the inner wall 13 of the fuel supply chamber.

Throttle 4 is mounted to hollow shaft 5 within the carburetor throat. The configuration of throttle 4 may be seen, by a comparison of the several 'figures, to comprise an element circular in plan aspect of less maximum thickness than the diameter of the shaft 5, except for collars 50 and 51, the plate being of gradually reduced thickness with distance from the shaft to provide relativelythin swinging edges remote from the shaft. The shaft 5 passes along a diameter of the circular throttle element and so divides the element that portions of the shaft surface are exposed through each face of the ,element. Split collars 50 and 51 are formed as a part of the throttle element at opposite ends of the diameter along which shaft 5 passes,and these collars surround and clamp. to the shaft to retainthe throttle in position thereon. Clamping bolts 52 and 53 draw the collars 5 0 and 51, respectively, tight on the shaft, and the bolts are operable by a wrench which may be introduced at air inlet portion 2 to loosen the bolts for adjustment of the rotative position ofthe throttle on the shaft, the bolts being thereafter tightened to lock the throttle in its desired adjusted position.

The throttle shaft 5 is seen to be hollow through the throttle element 4 and to the end of the shaftto' which arm 11 is attached. The end of the shaft at link 9 is closed. A plug, not shown, may be employed to close the link end. of the shaft, or the shaft may be formed from a solid rod longitudinally drilled from the arm end to form an internal passage into and through the position of the throttle. suppliesfuel to atomizing or distributing ports 55 opening from the passage 54 into the air stream below the throttle 4 in its idling or partially open position, the supply of fuel being restricted by a needle valve adjustable by screw 23. Passage 54 communicates with fuel supply passage 20 of arm 11, and it will be seen that, in the absence of air flow through the carburetor, the fuel stands at the level 56 in passage 20, as controlled by float 30. Passage 20 is in communication with groove 22 through its lower horizontal portion 41, and the groove 22 will be seen to be of tapering or gradually increasing depth in accord with the broken line 57 defining the portion of the groove extending from the lowermost portion shown in Fig.3. A normally empty portion 58 of the fuel supply .chamber exists above hub 24 of the fuel supply chamber and this normally empty portion communicates through a small orifice 27 in plate 14 with the upper portion, within hood 37, of float reservoir 28. During acceleration, upon forward motion of arm 11, the portion 58 of the fuel supply chamber will be filled with fuel under appreciable pressure and a suitable portion of this fuel, but obviously only a small portion, will be ejected back into the float reservoir through orifice 27,

while the major flow from the upper part of the chamber will be through an accelerating nozzle 59 into the air stream. The size of orifice 27 is proportionedto control the amount of the accelerating charge which will be delivered, and if too great a charge is found to be delivered, the orifice 27 maybe reamed to a larger size. Nozzle 59 is in communication with the portion 58 ofthe fuel supply chamber, and the member comprising the nozzle extends upwardly into channel 38 formed in the carburetor body 1. As heretofore mentioned,.channel 38 communicates betweenthe air passage of the carburetor, at

The passage 54 thus formed in shaft 5' its air inlet portion 2, and the reservoir 28. The nearly atmospheric air pressure at the intake portion 2, accordingly, is transferred to the volume above the fuel level in reservoir 28 and from reservoir 28 through orifice 27 to the volume above the fuel level in. the fuel supply chamber. As heretofore explained, fuel is introduced into reservoir 28 through a suitable fuel line coupling 36 and through a control valve 31, the valve being controlled by the position of valve control ball 32 as regulated automatically by the position of float 30. Ball 32 is prevented from falling out of the lower end of valve body 31 by the provision of post 34 which contacts the bottom wall of reservoir 28 to prevent dropping of the float 30 below a predetermined position. The location of flap or feather valve member 19 in open position is indicated in Fig. 3, and it will be understood that communication between reservoir 28 and the fuel supply chamber is through the port controlled by member 19 and through a second open port 17, each of which has been heretofore described. Plate 14 is held against recessed surface 16 by portions of reservoir member 28 which extend inwardly over the edges of the plate. Gasket 29 also overlies edge portions of plate 14, since the gasket conforms to the flange of reservoir member 28.

Fig. 4 is an end view of the carburetor taken from the fuel reservoir end, parts being broken away to disclose certain features of the internal construction. Fuel inlet line 60 provides fuel through coupling 36 into reservoir 28 under the control of ball 32 which engages portion 33 of the supporting hinge for float 30. Fuel from the float reservoir may pass freely through the port 17 in the plate 14 into the rearward compartment of fuel supply chamber 12, which lies behind rear face 47 of arm 11. Fuel may also pass through port 18 under the control of feather valve member 19 into the forward compartment of chamber 12 ahead of face 45 of arm 11; The fuel is furnished from the supply chamber into passage 54 of shaft 5 through longitudinal passage 20 of arm 11, and access of the fuel to the passage 20 is through the portions of channel 22 lying immediately ahead-of an behind the opening of passage portion 41. Channel 44 formed near the lower end of arm 11 communicates between the chamber in advance of forward face 45 of the arm and a portion of the groove 22 immediately behind passage 41. During constant speed operation when arm 11 and the throttle member 4 are stationary, fuel flows into channel 22 from the compartments both ahead of and behind arm 11. The restriction imposed by the groove on the flow into passage 41 is considerably greater when the throttle is near idling position and when the arm 11 is adjacent port 17 than when the throttle is further opened and arm 11 is near port 18, since groove 22 varies both in width and depth from a narrow and shallow size at its end near port 17 to a wider and deeper size adjacent the port 18 end.

Accelerating forward motion of arm 11 causes the fuel in the compartment in advance of forward face 45 of arm 11 to be increased in pressure, while the pressure within the compartment behind rear face 47 will remain almost constant or decrease very slightly, because port 17 is open at all-times. Except for the provision of channel 44, accelerating conditions would tend to cause a flow of fuel through groove 22 from the forward compartment to the rearward compartment past the opening of passage 41. The aspirating effect of such flow would stop or reduce the flow of fuel into passage 41. The provision of channel 44 causes the introduction of a desirable flow of fuel under pressure into channel 22 immediately behind the opening of passage 41 during acceleration, and the result is that fuel under more than normal pressure then flows into channel 41 from groove 22 from both directions. During acceleration, accordingly, channel 44 eliminates the tendency to drain channel 22 which would otherwise exist. Channel 44 serves an additional purpose during deceleration. Pressure within groove 22 might tend to build up as the arm swings toward port 17 under deceleration conditions, but bypass channel 44 reduces the pressure in the channel in the area immediately adjacent the opening of passage 41 toward which the opening is moving.

Fuel flows freely through port 18 into the forward compartment of chamber 12 during constant power and deceleration periods, but upon acceleration, feather valve flap member 19 seals off port 18 to permit the fuel ahead of arm 11 to be increased in pressure. This increase of pressure forces fuel up into the normally empty upper portion 58 of the fuel supply chamber and through accelerating nozzle 59 into the air stream. The vane 25 extending from hub 24 of arm 11 seals in a running fit against the walls 26 of the chamber portion 58 and permits fuel pressure in the forward compartment and in portion 58 to build up substantially above the approximately atmospheric pressure within the rearward compartment behind face 47. The fuel under pressure in chamber portion 58 provides a suitable accelerating charge of fuel through nozzle 59 into the air stream. It will be noted in Fig. 4 that channel 38 is only partially filled by nozzle 59, and that free air communication through channel 38 is not-appreciably affected by the provision of the nozzle.

The knob 61 of a vacuum control plug is also seen in Fig. 4, the purpose of which will be more particularly described hereinafter in connection with Fig. 6.

Fig. 5 is a top view of the carburetor, partially broken away, and disclosing the position of the throttle 4 and ports 21 as presented to the air entering upper portion 2 of the carburetor air passage. Control knob 61 is provided to adjust valve member 62 which controls the idling and low speed air-fuel ratio by bypassing air around the throttle through passages 63. In the idling range, the valve member 62 provides much of the control. The groove 22 is shallow and varies little in the low speed range, whereas the effect of passages 63', 63" changes substantially with a small change in throttle position in the low speed range. Plug 64 is shown as closing a single passage 65 communicating with the carburetor throat just above the position of the throttle at full idling position, and the passage 65may be used, by removing the plug 64, to provide an automatic spark control vacuum line connection if desired. The arrangement of link 9 to clamp stop member 6 to shaft 5, and the arrangement of protrusion 7 of the stop member, which may engage full throttle adjustment screw 8, are clearly seen in Fig. 5. The relative positions of reservoir 28 and of the fuel supply chamber within portion 66 of the main carburetor body, as held together by bolts 67, with interposed gasket 29, are shown, and it will be noted that hood portion 37 of the float reservoir 28 aligns with a projecting portion of the carburetor body into which the accelerating nozzle extends, and through which equalizing communication between the approximately atmospheric air pressure in portion 2 of the carburetor air passage and the upper portion of reservoir 28 is established.

Certain members of the carburetor which have been previously fully described are identified in Fig. 5 for purposes of comparison, and it will be understood that elsewhere in the drawings symbols have been applied to parts shown in certain figures without specific description in connection with the particular figure to assist in comparing the several views. Throughout the drawings, like symbols have been employed to designate like elements or portions.

Figs. 6 and 7 are sectional end views taken substantially transversely of throttle shaft 5 at the center of the carburetor air passage, Fig. 7 being fragmentary and diagrammatic in part.

Fig. 6 discloses conditions which may exist when protrusion 7 of the stop member is in contact with idling ad justment screw 48. At this time, throttle 4 may be horizontal, or substantially horizontal, and air may be passing into upper ports 21 and into channel 54 of the throttle shaft, to force a mixture of vaporized fuel and air downwardlythrough lower fuel delivery or atomizing ports 55. Additional air may .'be supplied by a bypassing channel system, through 63 communicating with the air passage above throttle 4 and out through passage 63" into the air passage below throttle 4. The amount of air supplied through bypassing passages 63, 63" is controllable in accord with the position of vacuum control plug 62 as adjusted by knob 61. Spring 68 is provided to prevent creeping of plug 62 from the manually adjusted position of the plug. The connection of throttle 4 to shaft 5 by means of collar 51, tightened by bolt 53,, which pulls collar end 69towar'd the lower face of throttle plate 4, is apparent in Fig. 6. 7

The conditions existing with closed throttle as shown in Fig. 6, wherein air indicated by'arrows 70 flows into upper ports 21 and flows downwardly toward the intake manifold carrying atomizedfuel through lower ports 55,

as indicated by arrows 71, continue to exist as the throttle is moved into partially open position. As the throttle opens, however, air'may pass around the edges of the throttle plate remote from shaft 5, and air flow around these edges, of 'coursejincreases a'sthe throttle is further opened. At about three-quarters throttle, or shortly theretofore, fuel begi'nsto be discharged from both ports or orifices 21 and 55, as indicated'by the arrows 72in Fig. 7.

Fig. 7 disclosesthe throttle position at full throttle, and the stream of fuel from ports 21 and 55, under full throttle condition, will be substantially equal and, of course, relatively large amounts of fuel will be supplied. .The tapered shape of throttle 4, as seen in' Fig. 7, provides a decreased throat area at'the level of the shaft 5, thereby to increase the venturi action at'thi's point. The orifices 21 and 55, while shown to beall of equal size, may be of different sizes. For example,if it is desired to provide a richer stream toward one side-of the throat than toward the other side, the ports towardthe corresponding respective one end of the shaft 5 within the throat may be made larger than the ports toward the otherend'of the shaft.

Since fuel issupplied through the shaft for introduction into-the air stream exactly at the throttle level, the turbulence created by the throttle in the air stream appreciably assists in forming a homogeneous and thorough dispersal of the fuel in the air stream.

Under idling conditions, with the throttle 4 horizontal, or nearly horizontal, and substantially closing the main air passage, air enters the uppervaporizing ports 21, as

seen in Fig.6, and carries fuel with it in passing on through the lower vaporizing ports 55 into the intake manifold. A pressure differential of about or 21 inches of mercury will normallyexist between the nearly atmospheric pressure. inthe intake portion 2 above the throttle and the partially evacuated passage below the throttle which connects with the intake manifold. The position of the arm in respect to the groove at idling throttle position is alternatively adjustable by changing the idling position of the throttle shaft, conveniently by adjustments to idling adjustment stop screw 48. Such adjustments to the stop screw 48, of course, also changes the idling position of the throttle 4, and thereby affect the amount of air flowing around the throttle. Separate adjustments are provided for altering the position of the throttle on the throttle shaft, and this is accomplished by means of bolts 52 and 53 which may be loosened to permit the throttle to be manually adjusted to a desired position on the shaft by inserting a suitable tool down through the air intake portion 2. After such adjustment, the throttle is again locked on the shaft by tightening bolts 52 and 53. The amount of air passing the throttle through low speed air bypass passages 63' and 63" is also adjustable and knob 61 and valve screw 62 are provided for this purpose. By a combination of adjustmentsto idling adjustment stop screw 48, adjustments to the position of the throttle'4. on itslsh'aft and'adjustments to'air bypass valve screw. 62, a wide range of adjustment of theair-fuel ratio atidling and-low speed is permitted' Since fueLduring idling,'is freely. admitted through ports-17 and 18 from the float reservoir into the fuel supply chamber, .under the atmospheric or nearly atmospheric pressure which'is. maintained in the fuelsupply chamber and fuel reservoir *throughchannel 38 from the intake portion 2'of'the main air passage, and since the gasoline level with constant throttle .is' normally just below the level of the throttle shaft, nearly.2l inches of mercury of pressuredifference..isapplicableZto force gasoline from the'ports .55.. iActualimeasurement indicates that the pressure differential: is. such that the pressure within the hollow interior of 'the throttle shaft and through passage 20 is about 16 inches of mercury below atmospheric pres sure. Accordingly, it will be seen that the principal meter ing of the gasoline, or other fuel, occurs atthe groove 22.

It is an'important feature of the carburetor of this invention that the pressure differential which causes the fuel to flow from the supply chamber into the air stream is very much greater than in priorart carburetors. The metering of fuel does; not depend primarily on small pressure changes, and the rate of fuel flow is not appreciably altered by atmospheric pressure changes, for example. Under constant power, or steady state, conditions,

the size of the groove 22 at'the' arm '11 is controlling'for lower power: settings, while for higherpowersettings, the maximumfuelfsupply'rate may be limited by theadjustable screw controlled-yalve 23', orby the size of groove 22,- or by the sizc i of thepassage 41. In the preferred arrangement, groove 22-ismade larger than passage 41, and the 'size'ofpassage -4l liinits the maximum fuel supply rate. i If, inoperatiomthe maximum rate is found to be too great for the particular engine with which the carburetor is being used, screw 23 is adjusted to limit the maximum rate by fimposing addition restriction at screw 23. It is to be noted that all of -the ports 21 and 55, on respective op'positesides of the throttle shaft, come into fuel supplying operation when the throttle is opened beyond about three-quarters throttle position. Accord ingly, the total 'are'a'of all of the-ports 21 and 55 becomes available for the supplying offuel at the maximum rate and at no time, preferably, is the'rate of flow metered by theavailable area of the vaporizing ports.

Upon rapid move'm'entof the throttle link'9 in an accelerating direction, important changes take place. The arm 11 moves toward-the wider and deeper end of groove 22, thereby providingflless restriction to the flow of fuel into the throttle shaft for vaporizing into the air stream through ports 21 and 55, feather valve 19 closes to seal port 18, and the pressure within the fuel supply chamber 12 ahead ofarrn ll increases. The increase in pressure forces'fuel into the upper portion 58 of the fuel supply chamber and fuel is thus ejected from nozzle; 59 into the air stream.. Since the rear compartment of the fuel supply chamber 12 behind arm 11 is in'communication with the float reservoir through relatively large open part 17, the fuel pressure behindarrn" 11 remains nearly at atmospheric pressure, and the net effect is that fuel is forced into passage 41 and passage 20 of the arm at more than atmospheric pressure. During the forward accelerating motion of arm 11, some fuel will be forced backthrough the small aperture 27 in wall plate 14 into the float reservoir, but aperture 27 is sufliciently small to pass, ordinarily, only a relatively small amount offuel during the relatively brief period of acceleration; 1 The'aperture 27, therefore, serves as a bypasswhich is proportioned in size to provide a desired amountof accelerating fuel. Alteration of'the size of aperture 27' will, ofcourse, alter thelamount of fuel supplied in any given accelerating movementof the QSGLGSC? the forward face 45 of arm 11 and communicating with the groove 22 immediately behind opening 41 at the lower end of passage 20 performs a useful function in supplying fuel from the forward compartment at substantially the pressure existing therein to the groove 22, whereby opening 41 receives fuel through groove 22 from both directions under the increased pressure of the forward chamber during acceleration periods. In the absence of channel 44, the forward movement of the arm and sucking of fuel from passage 29 would tend to drain channel 22 and substantially reduce the fuel pressure in groove 22 behind opening 41. It will be understood that channel 44 is primarily effective during relatively rapid motion of arm 11.

Channel 44 provides another and different function during rapid accelerating motion of arm 11 in preventing the build up of pressure in groove 22 in the portion of the groove toward which the arm is moving, by bypassing fuel from the point of communication of channel 44 with the groove out through the face 45 of arm 121. Thus channel 44 serves to increase the amount of fuel supplied through channel 20 to ports 21 and 55 during rapid accelerating movement of the arm and to overcome any tendency to supply increased fuel through passage 29 upon rapid decelerating movement of the arm. Gradual acceleration does not require an extra accelerating charge and none is provided, since gradual accelerating motion of arm 11 is insuflicient to cause feather valve 19 to close and no accelerating charge is forced through nozzle 59 or through passage 20.

As the throttle is opened toward full throttle position, the streamlined form of the throttle element 4 causes the throat of the air passage more nearly to approach venturi form. The action of the ports 21 in supplying gasoline to the air stream changes at approximately three-quarter throttle position from the admission of air into the hollow throttle shaft to the ejection of fuel into the air stream. Thus, at full throttle position, with the throttle member 4 subsantially vertical, approximately equal streams 72 of fuel will issued from ports 55 and 21 on opposite sides of the throttle shaft.

When the throttle is at other than full throttle position, at least the larger portion of the fuel will be introduced through the ports 55 into the air stream below the throttle. Turbulence in the area below the throttle is sufiicient to cause thorough dispersion of the fuel particles into the air stream and the action of the throttle is, accordingly, such as to provide improved fuel mixing under all conditions, it being understood that the spray produced by air passing into ports 21 and, mixed with fuel, out of ports 55, during idling conditions, provides good dispersion, and that the six sprays of fuel emerging from the throttle in fully open position similarly provides even distribution of the fuel throughout the air stream. If other than even distribution of fuel is desired, the ports 21 and 55 may be of different sizes.

Particular advantages of the carburetor of this invention, in accord with the above description include the following features. Simplicity and sturdiness of the parts are achieved, together with relatively large tolerance, as will be apparent from a consideration of the drawings. The seal or fit of fuel supply arm 11 against the opposite fiat walls of the sectoral fuel supply chamber is not critical in that leakage around the arm, between the forward portion and rearward portion of the chamber as divided by the arm, has no effect under constant power conditions and very little effect during decreasing power operation of the throttle. Upon accelerating forward movement of the arm 11, an accelerating charge is furnished through accelerating nozzle 59, as well as through the ports 21 and 55, and even substantial leakage past the arm decreases the amount of the charge very little. While leakage around the arm is not desired, and while the running fit of the arm against the walls is made a reasonably 10- close fit to provide as complete a seal as possible within the tolerances of inexpensive manufacture, satisfactory operation of the carburetor is obtainable even though the fit of the arm is so loose as to permit considerable leakage during accelerating motion of the arm.

No choke is required in the carburetor since a mere pushing down of the accelerator delivers a starting mixture of increased richness through the accelerating nozzle and because of the highly effective atomization and mixing of fuel with incoming air which results particularly from the arrangement of the ports 21 and 55 at the throttle. It will be seen, also, that no separate idling system is necessary; the fuel during idling enters the air stream through the passages and ports which are used in power operation.

It is not necessary to provide delayed throttle closing to prevent stalling of the engine with the present carburetor, since there is no loading of the carburetor under any operating conditions or sequence of operations. When the throttle closes, both air an fuel are cut off and only the idling mixture can enter the intake manifold, the fuel being metered through the small end of groove 22 and the air being metered through ports 21 and 55 and bypass passage 63, 63".

During closing movement of the throttle, feather valve member 19 provides some restriction to the how of fuel into the forward compartment of the fuel chamber, and the port 18 at the feather valve being somewhat smaller than the open port 17 into the rearward compartment, the pressure behind the arm 11' remains substantially atmospheric while the pressure in the forward compartment drops slightly below atmospheric. The net effect is that fuel flow into the air stream is reduced as the throttle closes, and no pumping of fuel into the air stream occurs with swinging of the arm 11 toward the closed throttle position. Centrifugal force on the fuel in metering groove 22 upon very rapid closing of the throttle further tends to prevent pumping upon rapid deceleration.

The carburetor clears itself of water and obstructing particles with ease and rapidity. The ports 17 and 18 into the fuel supply chamber are large enough freely to pass foreign matter. The pumping action associated with swinging of arm 11 tends to clear matter from the groove 22 and from about the opening into passage 41, and further causes flow back and forth through channel 44 to clear the channel. The pumping action is similarly effective to free other parts of the system.

The carburetor is not sensitive to fluctuations in float reservoir fuel level resulting from bumps, tilting, or the like, nor is it subject to surges from negotiating curves in an automobile, for example. The arrangement is such that the fuel, being confined in relatively small chambers, does not spill over from one part of the carburetor to another in any manner which will adversely effect operation. The connection provided between the upper portions of the chambers and the air intake portion of the barrel, together with the large pressure difference which causes the fuel to fiow into the air stream, greatly reduce or eliminate offside enrichment of the mixture and malfunctioning from changes in altitude or barometric pressure.

The groove 22 is preferably proportioned to be small throughout approximately one-quarter of the full arm movement distance at the low-speed end of the groove, and gradually to increase in size toward its full throttle end. The first one-quarter of throttle motion, according- 1y, changes the fuel supply rate primarily as a result of motion of the throttle member with respect to bypass passage 63, 63". Thereafter, the gradually increasing size of groove 22 meters the gradually increasing fuel rate, while the opening throttle increases the amount of air passing into the intake manifold.

While I have shown and described only certain preferred embodiments of my invention by way of illustration, many modifications will occur to those skilled in 1 the art, and I therefore wish to have it understood that said nozzle opening through said face, a closed fuel supply chamber-having a wall, an arm lying against said wall,

pivotal mounting means to, swing said arm across said wall, said arm having an opening thereinto from a portion toward said wall, said opening tracing an arcuate path across said wall with pivoting of said arm, said wall being grooved along said path, the size of 7 said wall groove increasing gradually from a small size at one end to a relatively larger size at the other end, said arm and said means comprising a fuel conduit communicating between said arm opening and said nozzle, said mounting means being connected to open said throttlerwtih swinging of said arm in the direction to dispose said arm opening toward said other end of said groove..

2. A downdraft carburetor having a main air passage comprising a constricted throat portion, a throttle diss posed in said portion and having a fuel supplying aperture, a sectorial fuel supply chamber comprising a sectorial wall, an arm connected to said throttle and disposed against said wall and movable swingingly in 7 said chamber and across said wall about the axis of said throttle, isaid arm having an opening toward said wall and remote from said axis, whereby said openingtraces an arcuate path along said wall with swinging of said arm, said arm having an internal passage communicating between said opening and said aperture, said wall having a surface groovealong siad path of a size gradually in creasing with distance from one end thereof'to the other, means to supply fluid fuel to said chamber for metering through said groove into said opening and arm passage, said arm dividing said chamber into a forward compartment and a rear compartment of respective volumes which vary inversely to one another with swinging of said arm, said forward compartment lying toward said other end of said groove and said rear compartment lying toward said one end of said groove, a check valve, said fuel supply means comprising a fuel reservoir communicating freely with said rear compartment and communicating through said check valve into said forward compartment, and an accelerating nozzle having a closed conduit connecting directly with said forward compartment and operative to supply an accelerating charge of fuel to said air passage in response to increased fuel pressure in said forward compartment produced by rapid swinging of said arm in'the direction to decrease the volume of said forward compartment.

3. In a downdraft carburetor, a main air passage having a constricted throat portion, a throttle at said throat portion, a conduit into said throttle and having a port to admit fuel from said conduit into the air stream at said throttle, said port opening from an under portion of said throttle subject to at least substantially one-half of the full intake manifold vacuum, when. said throttle is in idling position, a fuel supply chamber comprising a wall having an elongated groove of a size gradually increasing from one end to the other of said groove a fuel receiving member having an internal passage communicating at one end with said conduit, said receiving member having an opening into the other end of said passage means to move said member to sweep said opening along said groove, said last means being responsive to throttle movements, whereby said opening is positioned at'points on said groove corresponding with respective settings of said throttle.

4. A downdraft carburetor comprisnig an air passage 12 having a throat area, a throttle in 'saidarea having upper and lower major faces disposed generally horizontally across said throat at idling settings, a hollow throttle shaft mounting said throttle and having apertures into said air passage from the hollowinterior of said shaft through said lower major face, means to rotate said shaft and throttle between different power settings, afuel supply arm mounted externally of said air passage on said shaft and swingable with rotation of said shaft, said arm having a fuel supply passage communicating with the hollow interior of said shaft, wall means defining 'a closed fuel supply chamber housing said arm and comprising a wall traversed by said arm in accord with throttle shaft rotation, said arm having an opening through a portion thereof which lies against said traversed wall, said opening communicating with said fuel supply passage of said arm, said wall having an elongated groove extending along the path traversed by said opening with said swinging of said arm, said groove being of a size gradually increasing with distance from one end to the other of said path.

5. In a downdraft carburetor comprising a sectorial fuel supply chamber, a hollow throttle shaft having ports to expel fuel from the hollow interior of said shaft into the main air stream, and an arm disposed in said chamber and connected to swing with rotation of said shaft and having a longitudinal passage communicating with said hollow interior of said shaft, a side of said arm being arranged to contact and sweep across an inner face of' said chamber and having an opening toward said face communicating with said passage, said opening being positioned to travel an arcuate path across said face in response to said shaft rotation, the provision in said face of a groove along the full extent of said path tapering in cross-sectional area from an area much smaller than that of said opening at one end of said groove gradually to an increased area of at least substantially as great as the area of said opening at the other end of said groove, the portion of said arm contacting said face having a back edge spaced from said opening toward one end of said groove and having a forward surface extending outwardly from said wall and facing generally toward said other end of said groove, and a bypass passageway opening at one end through said portion of said arm, said one end opening being located between said edge and said first opening and being directed and disposed to open into said groove and said bypass passageway communicating between said first end opening and said second end opening 'which is located to open through said forward surface.

6. In a downdraft carburetor having a constricted throat air passage, a throttle member, a rotatable control shaft for said throttle member, a fuel nozzle opening into said air passage at said throat and below said throttle when said throttle is in idling position, a fuel supply systern including a fuel reservoir and channeled means comwith said movable member for movement therewith, said taper being proportioned gradually to increase the restriction to the flow of fuel to said nozzle in response to throttle closing rotation of said shaft and gradually to decrease said restriction in response to throttle opening rotation of said shaft.

7. "A downdraft carburetor comprising a main air passage having a constricted throat portion, a throttle member in said throat portion, a plurality of nozzles enteraeonose ing at said throat portion subject at idling settings of said throttle to substantially full intake manifold vacuum, a fuel supply chamber having an upper opening communicating with a source of at least substantially atmospheric pressure, and means to furnish fuel from said chamber to said nozzles, said means comprising a continuously and gradually variable restrictor valve controlling a restriction to the flow of fuel through said means, said restrictor valve being connected to said throttle member for operation therewith and being arranged gradually to reduce the restriction to fiuel flow with gradually increasing power settings of said throttle member and gradually to increase the restriction with gradually decreasing power settings of said throttle member.

8. A downdraft carburetor comprising a main air passage having a constricted throat portion, a throttle member in said throat portion, a plurality of nozzles entering at said throat portion subject at idling settings of said throttle to substantially full intake manifold vacuum, a fuel supply chamber having an upper opening communicating with a source of at least substantially atmospheric pressure, means to furnish fuel from said chamber to said nozzle, said means comprising a continuously and gradually variable restrictor valve controlling a restriction to the flow of fuel through said means, said restrictor valve being connected to said throttle member for operation therewith and being arranged gradually to reduce the restriction to fuel flow with gradually increasing power settings of said throttle member and gradually to increase the restriction with gradually decreasing power settings of said throttle member, said valve comprising a member movable in said chamber, with opening movements of said throttle member, toward an end of said chamber to tend to increase the pressure of the fuel in the portion of said chamber toward said end, said chamber having an outlet accelerating charge conduit communicating from said end portion to said air passage, said end portion having an inlet and pressure equalizing port and a normally open check valve member arranged to seal said port upon rapid increase in pressure in said end portion in response to rapid motion of said throttle member and of said member movable with said throttle member toward said end, said port being effective to maintain normal pressure in said end portion during slowly increasing throttle movements and during decreasing movements and during stationary periods of said throttle member.

9. A downdraft carburetor comprising a main air passage having a constricted throat portion, a throttle in said throat portion, means to rotate said throttle between an idling position and a full throttle position, said throttle having an upper major face disposed toward the inlet of said air passage at idling throttle position and at full throttle facing generally toward a side of said air passage, said throttle having a lower major face opposite said upper face, said means comprising a hollow shaft extending into said throttle, said throttle having an opening extending therethrough from said upper face to said lower face and communicating with the hollow interior of said shaft, and means to supply fuel to the hollow interior of said shaft, said last means comprising a continuously and gradually variable fuel flow restricting mechanism connected to said first means and operable gradually to increase the restriction to the flow of fuel in response to gradual rotation of said throttle toward said idling position and gradually to decrease the restriction in response to gradual opening of said throttle.

10. In a downdraft carburetor, a fuel supply chamber, a movable piston member in said chamber, said chamber having a fuel inlet port in a wall thereof, said piston member being arranged to increase the pressure of fuel in a portion of said chamber which includes said port in response to motion of said member in a predetermined direction, a feather valve member disposed to cover said port in response to said increased pressure and to uncover said port for the admission of fuel to said chamber in the absence of such increased pressure, fuel metering means connected with said piston member variably to restrict the flow of fuel from said chamber in accord with the position of said piston member in said chamber, means forming a main air passage having a constricted throat portion, an accelerating nozzle in said air passage con nected to said portion of said chamber, a second nozzle at said throat portion, a throttle in said air passage, means to supply fuel through said metering means to said second nozzle, and means to operate said throttle between greater and less power positions and concurrently and correlatively to move said piston in said chamber, said second nozzle opening into said throat below the idling position of said throttle.

11. In a downdraft carburetor having an air passage, a throttle in said passage, a fuel supply nozzle opening into said passage on the intake manifold side of said throttle, operating means for said throttle, a chamber, means to supply fuel to said chamber, a movable member in said chamber connected to said throttle operating means for movement therewith, and a fuel conduit connecting between said nozzle and said chamber and terminating in a fuel receiving orifice in said chamber, said chamber and said member comprising cooperating means variably to restrict the flow of fuel into said orifice in accord with the position of said member in said chamber.

12. In a downdraft carburetor, an air passage having a constricted throat, a nozzle positioned to supply fuel into said air passage at said throat, a throttle control member, a fuel chamber having a wall, a piston member connected to said throttle control member for movement in said chamber along said wall thereof and having a passage communicating at one end with said nozzle and at its other end opening from said piston member toward said wall, whereby said passage opening traces a path along said wall with said movement of said piston member, said piston having a forward face and being arranged to increase pressure at said face within a forward portion of said chamber in response to movement of said piston member in a predetermined forward direction, said wall having a groove tapering along said path cooperating with said opening, and a bypass channel in said piston member connecting between a first opening of said channel through said forward face and a second opening of said channel toward said wall into said groove, said second opening of said channel being spaced from said forward face by a greater distance than said first mentioned passage opening, whereby said channel opens into said groove behind said passage opening.

References Cited in the file of this patent UNITED STATES PATENTS 1,126,127 Swan Jan. 26, 1915 1,325,688 Burr Dec. 23, 1919 1,383,044 Welland June 28, 1921 1,801,684 Oelerich Apr. 21, 1931 2,214,273 Fish Sept. 10, 1940 2,236,595 Fish Apr. 1, 1941 2,463,535 Holley Mar. 29, 1949 2,617,638 Udale Nov. 11, 1952 FOREIGN PATENTS 611,784 France July 17, 1926 

